The present invention relates to a fusion-splicing method for splicing optical fibers, a cleaving apparatus for cleaving the tip of optical fibers, a fusion-splicing apparatus for splicing optical fibers which have been cleaved at the tip thereof, and an optical fiber holder.
As a method for splicing optical fibers, a fusion-splicing method has been practiced. This fusion-splicing method consists of the following three steps. The first step involves stripping the coating from the tip of the optical fiber using a stripping apparatus called stripper (remover). The second step comprises cleaving the optical fiber thus exposed to a predetermined length using an optical fiber cleaving apparatus. The third step comprises fusion-splicing the optical fibers with the tip thereof abutted to each other using a fusion-splicing apparatus.
In the fusion-splicing step, electric discharge starts while the tip of the optical fibers are kept at a predetermined distance and positioned at the fusion starting position. Subsequently, one or both of the optical fibers are pushed in a direction such that the distance between the tip thereof is reduced. Thereafter, the tip of the optical fibers are spliced at the fusion end position to complete fusion-splice. There are two methods for positioning the tip of optical fibers to each other. The first method comprises positioning the coated portion of the optical fiber in the vicinity of the tip thereof with the optical fiber exposed at the tip thereof using a V-groove. The second method comprises positioning the exposed optical fiber itself using a V-groove. In any of these methods, positioning of the tip of the optical fiber must be conducted precisely.
FIG. 9 is a diagram illustrating a structure for supporting an optical fiber in a conventional fusion-splicing apparatus. In FIG. 9, only a mechanism for supporting one of the two optical fibers is shown. In FIG. 9, the reference numeral 1 indicates a coated optical fiber, the reference numeral 1a indicates an optical fiber, the reference numeral 31 indicates an optical fiber holding table, the reference numerals 32a, 32b each indicate a clamping member, the reference numeral 33 indicates a slider mechanism, and the reference numeral 34 indicates a supporting table.
The optical fiber holding table 31 is provided with a groove (not shown) in which the optical fiber 1 having a protective coating is received. The optical fiber 1 received in the groove is clamped by the clamping members 32a, 32b. The optical fiber holding table 31 is supported on the supporting table 34 via the slider mechanism 33 in such an arrangement that it can move along the axis of the optical fiber 1 thus clamped. The supporting table 34 and the other supporting table (not shown) are disposed opposed to each other and are supported on the respective optical fiber holding table 31. These supporting tables are arranged such that they can be moved by the respective movement mechanism (not shown) to align the tip of the optical fiber 1a obtained by exposing the optical fiber 1.
Referring to the operation of this fusion-splicing apparatus, an optical fiber is set in a stripper. The optical fiber is then stripped at the tip thereof. Subsequently, the optical fiber is set in a cleaving apparatus. The optical fiber is then cleaved at the tip thereof. Thereafter, the optical fiber is set in the optical fiber holding table 31 of the fusion-splicing apparatus described in connection with FIG. 9 where it is then subjected to fusion-splice. However, the length (cleaved length) of the optical fiber thus cleaved is not constant itself. Since this fusion-splicing apparatus employs a procedure requiring the removal of the optical fiber from the cleaving apparatus and the transfer of the optical fiber to the optical fiber holding table 31, the position in the longitudinal direction of the optical fiber 1 clamped by the clamping members 32a, 32b is not constant. As a result, it takes much time to align the tip of the optical fiber. Further, since the optical fiber 1 is clamped at the tip thereof by the clamping member 32a, the coating may be curved if it is not sufficiently clamped. As a result, the position of the tip of the optical fiber 1a cannot be stably fixed with a good precision.
FIG. 10 illustrates an embodiment of the holder mechanism for fusion-splicing apparatus designed to improve the precision of fixing of an optical fiber. Like numerals are used for like parts in FIGS. 9 and 10. The description of parts similar to those of FIG. 9 will be omitted. In FIG. 10, the reference numerals 34a, 34b each indicate a supporting table, the reference numeral 35 indicates a V-groove member, and the reference numeral 36 indicates a clamping member.
As shown in FIG. 10, the V-groove member 35 and the clamping member 36 are provided besides the optical fiber holding table 31 for holding the optical fiber 1 and the clamping member 32a. The coated optical fiber 1 is clamped by the V-groove member 35 and the clamping member 36 at the position close to the tip thereof. In this arrangement, the clamping force applied to the coated optical fiber 1 at the position close to the tip thereof can be enhanced, making it possible to improve the precision of fixing of the optical fiber 1a. The V-groove member 35 is supported on the supporting table 34b. Another supporting table (not shown) is disposed opposed to the supporting table 34b. The optical fiber 1 clamped in the respective V-groove member 35 is then stripped at the tip thereof. These supporting tables are arranged such that they can be moved using the respective movement mechanism (not shown) to align the tip of the optical fiber 1a thus exposed.
In the fusion-splicing apparatus comprising the foregoing holder mechanism, when the optical fiber 1a is pushed by the slider mechanism 33 during fusion, the optical fiber holding table 31 moves forward. However, since the V-groove member 35 does not move, the optical fiber 1 makes sliding movement forward against the clamping force by the V-groove member 35 and the clamping member 36. Accordingly, when the clamping force is large, the optical fiber 1 can undergo buckling or cannot move through the V-groove, making it impossible to perform good splice. On the contrary, when the clamping force is small, the optical fiber 1 cannot be stably clamped.
FIG. 11 is a schematic diagram illustrating a holder mechanism described in Japanese Patent Unexamined Publication No. Hei. 9-113752. FIG. 11(A) is a schematic diagram. FIG. 11(B) is a sectional view of the fitting portion. Like numerals are used for like parts in FIGS. 9, 10 and 11. The description of parts similar to those of FIG. 9 will be omitted. In FIG. 11, the reference numeral 37 indicates a holder, the reference numeral 37a indicates a tapered pin, the reference numeral 38 indicates a holder mount, and the reference numeral 38a indicates a tapered hole.
Referring to the operation of this holder mechanism, the optical fiber 1 which has been stripped at the tip thereof is clamped in the holder 37. The holder 37 is prepared for each of the optical fiber 1 to be spliced. The holder 37 comprises the tapered pin 37a provided at the bottom thereof. At the holder mounting portion of the cleaving apparatus for cleaving the optical fiber 1a of the optical fiber 1 is provided a tapered hole in which the tapered pin 37a is fitted. In this arrangement, the holder 37 is positioned in the cleaving apparatus using the tapered pin 37a and the tapered hole. Accordingly, the cleaving position of the optical fiber is constant with respect to the holder 37.
In order to splice optical fibers to each other, the holder having the optical fiber 1 clamped therein is removed from the cleaving apparatus, and then mounted on the holder mount 38 of the fusion-splicing apparatus as shown in FIG. 11(A). The holder mount 38 has a tapered 38a formed at the position corresponding to the position of the tapered hole in the holder mount of the cleaving apparatus as shown in FIG. 11(B). In this arrangement, the length of the optical fiber thus cleaved is constant itself. In the fusion-splicing apparatus, too, the holder can be positioned and mounted on the holder mount 38, making it possible to mount the optical fiber 1a in such an arrangement that the tip thereof is always at a constant position.
However, since the coated optical fiber 1 is set at the position close to the tip thereof in the V-groove member 35, which has the same structure as described in connection with FIG. 10, there arises the same problems as described in connection with FIG. 10.
Further, since coated optical fibers 1 having an outer diameter of 0.25 mm, 0.4 mm, 0.9 mm, etc. are commercially available, the holder mechanism of FIG. 11 is disadvantageous in that the V-groove member 35 must be exchanged and adjusted according to the outer diameter of the coated optical fiber 1. In addition, in the case where the spliced portion is image-taken under microscope and then monitored on a monitor screen, the variation of the height of the central axis of the optical fiber 1 with the outer diameter of the optical fiber must be dealt with. In other words, every time an optical fiber 1 having an outer diameter different from that of the previous optical fiber is spliced, the position of the optical fiber or the height of the microscope or the position of the discharge electrodes must be adjusted.
In the foregoing embodiments, the coated portion of the optical fiber is clamped by a V-groove member. Similar problems occur with the case where the optical fiber stripped its coating is clamped by the V-groove member. In other words, since optical fibers 1a having an outer diameter of 80 xcexcm, 125 xcexcm, 150 xcexcm, 280 xcexcm, etc. are commercially available, the V-groove member must be exchanged or adjusted according to the outer diameter of the optical fiber in order to monitor the spliced portion without adjusting the height of the microscope even when optical fibers 1a having different outer diameters are clamped by the V-groove member.
The present invention has been worked out in the light of the foregoing circumstances. An object of the present invention is to provide an optical fiber holder, a fusion-splicing apparatus, a cleaving apparatus and a method for splicing optical fibers which can deal with coated optical fibers or optical fibers having different outer diameters and accurately positioning the tip of optical fiber during fusion-splice.
The present invention lies in an optical fiber holder which is used for a stripping apparatus, cleaving apparatus and fusion-splicing apparatus in common, comprising a holder main body having a groove for inserting an optical fiber therein and a clamping member for clamping the optical fiber inserted in the groove, and a V-groove portion provided ahead of the holder main body for inserting the optical fiber therein, wherein the V-groove portion is clamped by a clamping member which is mounted on a holder mount in the stripping apparatus, cleaving apparatus or fusion-splicing apparatus and which is compressed toward the V-groove portion by a spring member.
The present invention also lies in the foregoing optical fiber holder, wherein the optical fiber holder is prepared for each of a plurality of kinds of optical fibers having different outer diameters and the groove and the V-groove in the V-groove portion of each of the optical fiber holders are formed in such an arrangement that the central axis of the optical fiber clamped at these grooves are in the same position independent of the outer diameter of optical fiber.
The present invention further lies in a method for splicing optical fibers which comprises effecting a sequence of steps involving coating stripping, cleaning, cleaving and fusion-splice without removing the optical fiber from the optical fiber holder to splice optical fibers.
The present invention still further lies in a fusion-splicing apparatus having an optical fiber holder comprising a holder main body having a groove for inserting the optical fiber therein and a clamping member for clamping the optical fiber inserted in the groove and a V-groove portion provided ahead of the holder main body for inserting an optical fiber therein, and a holder mount for mounting the optical fiber holder thereon, characterized in that the holder mount comprises a positioning portion for positioning the optical fiber holder and a supporting portion for supporting the clamping member which is compressed toward the V-groove portion by a spring member.
The present invention still further lies in a cleaving apparatus having an optical fiber holder comprising a holder main body having a groove for inserting an optical fiber therein and a clamping member for clamping the optical fiber inserted in the groove and a V-groove portion provided ahead of the holder main body for inserting the optical fiber therein, a holder mount for mounting the optical fiber holder thereon, a cleaving blade, a V-groove member for inserting a coated optical fiber therein, and a clamping member for clamping the coated optical fiber inserted in the V-groove member, characterized in that the holder mount has a positioning portion for positioning the optical fiber holder and a supporting portion for supporting the clamping member which is compressed toward the V-groove portion by a spring member and the cleaving blade is positioned interposed between the V-groove portion and the V-groove member and is adapted to make a cleave on the optical fiber clamped between the V-groove portion and the V-groove member.
The present invention still further lies in an optical fiber holder which is used for a cleaving apparatus and fusion-splicing apparatus in common, comprising a holder main body having a groove for inserting an optical fiber therein and a clamping member for clamping the optical fiber inserted in the groove, and a V-groove portion provided ahead of the holder main body for inserting the optical fiber therein, wherein the V-groove portion is clamped by a clamping member which is mounted on a holder mount in the cleaving apparatus or fusion-splicing apparatus and which is compressed toward the V-groove portion by a spring member.
The present invention still further lies in the foregoing optical fiber holder, wherein the optical fiber holder is prepared for each of a plurality of kinds of optical fibers having different outer diameters and coated optical fibers having different outer diameters, the groove in the optical fiber holders are formed in such an arrangement that the central axis of the optical fibers clamped at these grooves are in the same position independent of the outer diameter of coated optical fiber and the V-groove in the V-groove portions are formed in such an arrangement that the central axis of optical fibers clamped at these grooves are in the same position independent of the outer diameter of coated optical fiber.
The present invention still further lies in a method for splicing optical fibers which comprises effecting a sequence of steps involving cleaving and fusion-splice without removing the optical fiber from the optical fiber holder in order to splice optical fibers.
The present invention still further lies in a fusion-splicing apparatus having an optical fiber holder comprising a holder main body having a groove for inserting an optical fiber therein and a clamping member for clamping the optical fiber inserted in the groove and a V-groove portion provided ahead of the holder main body for inserting an optical fiber therein, and a holder mount for mounting the optical fiber holder thereon, characterized in that the holder mount comprises a positioning portion for positioning the optical fiber holder and a supporting portion for supporting the clamping member which is compressed toward the V-groove portion by a spring member.
The present invention still further lies in a cleaving apparatus having an optical fiber holder comprising a holder main body having a groove for inserting an optical fiber therein and a clamping member for clamping the optical fiber inserted in the groove and a V-groove portion provided ahead of the holder main body for inserting the optical fiber therein, a holder mount for mounting the optical fiber holder thereon, a cleaving blade, a V-groove member for inserting a coated optical fiber therein, and a clamping member for clamping the coated optical fiber inserted in the V-groove member, characterized in that the holder mount has a positioning portion for positioning the optical fiber holder and a supporting portion for supporting the clamping member which is compressed toward the V-groove portion by a spring member and the cleaving blade is positioned interposed between the V-groove portion and the V-groove member and is adapted to make a cleave on the optical fiber clamped between the V-groove portion and the V-groove member.